Inquiry into Death of Kremlin Critic Will Examine Possible Involvement of Russian Authorities

LONDON—The deadly dose of radioactive material used to poison Alexander Litvinenko at a Mayfair hotel in 2006 may have been the second attempt on the former Russian spy’s life in two weeks, a British inquiry heard on Tuesday.

The revelation came on the first day of a long-awaited public inquiry into the circumstances of the death of Mr. Litvinenko, a former KGB officer who had moved to the U.K. in 2000 and become a Kremlin critic. The inquiry, which is expected to last nine weeks, is expected to aggravate relations...